Connecting elements of said type permit, in a known way, the generation of a module which contains for example a rocker arm as a cam follower and a support element With a module of said type, the risk of potential incorrect assembly in the cylinder head of the internal combustion engine is minimized. Said incorrect assembly could inter alia consist in that the rocker arm is mounted in the valve drive rotated through 180°. In this case, the contact partners the ball head of the support element and spherical cap of the rocker arm, and the valve shank end and corresponding mating surface on the rocker arm, would be interchanged. This would result at least in valve drive malfunction, and in the worst case, even in serious engine damage.
In contrast to connecting elements which engage in a form-fitting manner into an annular groove below the ball head, connecting elements which act in a frictionally-engaging manner can advantageously be used in cases in which the annular groove cannot or cannot economically be produced as an undercut. Further demands on a connecting element of said type are not only that a separation of rocker arm and support element by transport influences is reliably prevented, but also that the rocker arm and the support element remain aligned with respect to one another, corresponding to the operational state, by means of the connecting element even during the assembly of the module into the internal combustion engine. In this respect, the connecting element also performs the task of largely preventing the rocker arm from tilting about its longitudinal axis by means of suitable lateral support on the support element in order to ensure correct transverse alignment of the rocker arm on the camshaft which is to be installed. A tilting of the rocker arm about its longitudinal axis is referred to below as a tilting movement in contrast to its pivoting movement in the direction of the gas-exchange valve.
The prior art has already proposed connecting elements which are connected to the support element in a frictionally-engaging instead of form-fitting manner. U.S. Pat. No. 6,047,675 A, which is considered as being generic, discloses a connecting element which is composed of flat material and which is connected in a frictionally-engaging manner to a support element which has no undercut in the region of the spherical end. Said connecting element has projections which are aligned towards the cylindrical section below the spherical end and which engage around the support element in such a way that a tilting movement of the rocker arm which is mounted on the support element is largely prevented, while the pivoting movement of said rocker arm in the actuating direction of the gas-exchange valve is permitted.
The connecting element proposed in the cited document nevertheless has some significant disadvantages. For example, the projections of said connecting element are of flat design and extend merely in a plane parallel to the pivot axis of the rocker arm. This firstly has the result that a lever arm, which promotes the correct transverse alignment of the rocker arm on the support element, between the contact points of the projections and the centre of rotation of the rocker arm is disadvantageously small. Secondly, on account of the not only flat but also short projections, as a result of their limited material elasticity, it is necessary for the splaying of the projections, which is required for the assembly of the connecting element, to be imparted largely by means of elastic deformation of the webs from which the projections proceed. However, there is the risk here of an undesired warping of the webs, for example in the form of corrugation, torsion or twisting. Such deformation of the connecting element can likewise lead, on account of projections being offset in terms of height, to misalignment of the rocker arm. In connection with said short lever arm, there is additionally an increased risk of the connecting element slipping in the tilting direction of the rocker arm.
Said disadvantageous effect can be further intensified taking into consideration the component tolerances. The cause for this is likewise to be considered the planar, short and consequently comparatively rigid projections, so that both a production-related change in spacing of the projections relative to one another and also a fluctuating diameter of the cylindrical section as a result of additional deformation of the web sections from which the projections proceed must be compensated.
A rocker arm which is aligned correctly on the support element can finally be of significance not only for the transport and assembly of the module but also for fail-safe operation in the internal combustion engine. For example, in the event of a loss of contact between the rocker arm and the actuating cam, the action of the cam which aligns the rocker arm can be lost. Causes for a loss of contact of said type can be undesired subsidence of the most-used support elements with hydraulic valve play compensation, or lifting of the rocker arm from the cam as a result of an excessively high rotational speed of the internal combustion engine. In the phase of contact loss, a “skewed” connecting element would then force the rocker arm in the tilting direction. In this regard, rocker arms with a very narrow cam contact face are to be given particular consideration. These are used in multi-valve engines with restricted installation space or also in variable valve controllers in which a cam pack composed of a plurality of cams of different lift is movably mounted on its camshaft and is placed in engagement with the rocker arm by the cam suitable for the operating state of the internal combustion engine. The rocker arm is then at particular risk with regard to a further tilting movement or completely tilting away from the support element, since in the event of renewed contact with its cam, said rocker arm can no longer be aligned on the cam to a sufficient degree on account of the narrow cam contact face.